The engraving of dots on the surface of metallic or non-metallic workpieces is conventionally used for coding information, in particular for identification and traceability purposes. These engravings can in particular be produced by means of a laser, generating multiple burns, or by micropercussions executed on the surface to be marked. These technologies make it possible to engrave engravings by producing very small dots, typically of the order of 0.2 mm in diameter. This fineness advantageously enables the engraving on the marked workpiece to be made discreet.
To read engravings, it is known to illuminate the engraved surface by means of a monochrome or white diffuse circular light beam. Such lighting makes it possible to highlight the differences of thickness by illuminating the edges of the holes and bumps on the surface. This solution is effective on a plane and shiny surface and for reading engravings engraved by laser, but is not appropriate if the surface is impaired, that is to say if it is not completely smooth outside of the engraving zones.
It is also known to illuminate the surface by means of a monochrome or white light beam coaxial with the sighting axis, by way of a beam-splitting plate placed in the path of the sighting axis and of the lighting. With this solution, only the rays striking the surface elsewhere than on the engravings are returned toward the eye of the camera, thereby making it possible to reveal the black engraving dots on a white background. This solution, very effective for reading engravings on a plane and shiny surface, is not well suited if the surface is impaired or if it is not plane.
These solutions are also relatively ineffective when the relative position of the engraved surface with respect to the reading device is variable.
The risk of a reading error is further increased when the engraving to be read is produced on surfaces that may exhibit diverse forms (plane, concave or convex) or on surfaces that may exhibit very different surface states or else on surfaces whose nature may be variable.
Finally, the fineness of the engraving dots makes it tricky to read and decipher the engravings.
There therefore exists a requirement for a reading device making it possible to solve, at least partially, the abovementioned problems.
An aim of the invention is to meet this requirement.
1) “Basic” Invention